What is this? Mystery illness kills 18 in Nigeria

Saw this first in De Volkskrant.  A mystery illness kills 18 in Ondo, Nigeria.   It is not Ebola.   The Volkskrant piece (in Dutch) links to a BBC item, reporting blurred vision, headache and loss of consciousness and that lab tests have ruled out any virus.

So, what is it?   How would you tell?

I checked ProMED-Mail, a useful source of information about infectious disease outbreaks.  A search for Nigeria in the subject finds reports of "undiagnosed illness", with an item from 19th April reporting that it is not Ebola.   An item from 18th April (archive number 20150418.3306299) has the suggestion that it is methanol poisoning.

I also checked Healthmap, and a search for Nigeria as location finds it, and leads to this item from the Guardian  in which the WHO are reporting that the likely cause was weedkiller.  Not the usual Guardian that I cite, but one based in Nigeria.

I suppose it reflects anxiety, and the recent and ongoing Ebola outbreak in neighbouring countries that Ebola or infections were the first thought.  And the symptoms are quite general, in the sense that many illnesses have this sort of symptom.

I shall try to return to this for updates.